Power conversion device

Abstract

The invention provides a power conversion device which comprises an input positive end, an input negative end, an output positive end, an output negative end, N first circuit stages, N second circuit stages and N third circuit stages, and N is an integer larger than or equal to 2. The input negative terminal is coupled to the output negative terminal. Each first circuit stage comprises a pair of switches and a pair of energy storage elements which are electrically connected, the pair of switches are conducted in a complementary mode, and the pair of energy storage elements have opposite working states. A plurality of energy storage elements in the N first circuit stages divide an input voltage. The second circuit stage includes a pair of switches that are complementarily conductive. The third circuit stage includes a pair of electrically connected switches and a magnetic element. The N first circuit stages, the N second circuit stages and the N third circuit stages are sequentially cascaded between the input positive end and the output negative end.

Description

Technical Field

[0001] This case relates to a power conversion device, especially a power conversion device with a variable input-output voltage ratio. Background Art

[0002] In existing non-isolated power conversion applications, as the power density continues to increase, the energy that the converter needs to process also increases accordingly. Therefore, higher requirements are put forward for high input-output voltage ratio, high efficiency and miniaturized design.

[0003] In existing practices, power converters with a fixed input-output voltage ratio are mostly used, which can be divided into two categories: resonant converters and non-resonant converters. Although the non-resonant converter has a simple structure, it has disadvantages such as large switching losses, low switching frequency and limited power density, and it is difficult to meet the requirements of high power density. In addition, the resonant converter has lower switching losses due to its soft-switching characteristics. However, the resonant converter is usually only applicable to applications with a low input-output voltage ratio and cannot effectively meet the requirements of a higher input-output voltage ratio.

[0004] Therefore, how to invent a power conversion device that can improve the above-mentioned existing technologies is an urgent need at present. Summary of the Invention

[0005] The purpose of this case is to provide a power conversion device with a variable input-output voltage ratio. Since the input-output voltage ratio of the power conversion device can be adjusted according to actual needs, it can meet the requirements of high input-output voltage ratio and high power density.

[0006] To achieve the above purpose, this case provides a power conversion device, which includes a positive input terminal, a negative input terminal, a positive output terminal, a negative output terminal, N first circuit stages, a second circuit stage and a third circuit stage, where N is an integer greater than or equal to 2. The positive input terminal and the negative input terminal receive an input voltage. The positive output terminal and the negative output terminal provide an output voltage, and the negative input terminal is coupled to the negative output terminal. Each first circuit stage includes a pair of switches and a pair of energy storage elements that are electrically connected, and the pair of switches conduct complementarily, and the pair of energy storage elements have opposite operating states. Multiple energy storage elements in the N first circuit stages divide the input voltage. The second circuit stage includes a pair of switches that conduct complementarily. The third circuit stage includes a pair of switches and a magnetic element that are electrically connected. The N first circuit stages, the second circuit stage and the third circuit stage are cascaded between the positive input terminal and the negative output terminal in sequence.

[0007] To achieve the above object, the present case further provides a power conversion device, which includes an input positive terminal, an input negative terminal, an output positive terminal, an output negative terminal, N first circuit stages, a second circuit stage, and a third circuit stage. The input negative terminal is coupled to the output negative terminal. Each first circuit stage includes a first switch, a second switch, a first capacitor, and a second capacitor, and has a first connection terminal and a second connection terminal, where N is an integer greater than or equal to 2. The first ends of the first switch and the second switch of the first first circuit stage are both electrically connected to the input positive terminal. In any first circuit stage, the first end and the second end of the first capacitor are respectively electrically connected to the second end of the first switch and the first connection terminal, and the first end and the second end of the second capacitor are respectively electrically connected to the second end of the second switch and the second connection terminal. The second end of the first switch of the nth first circuit stage is also electrically connected to the first end of the first switch of the (n + 1)th first circuit stage, and the second end of the second switch of the nth first circuit stage is also electrically connected to the first end of the second switch of the (n + 1)th first circuit stage, where n is a positive integer less than N. The first connection terminal of the nth first circuit stage is electrically connected to the second connection terminal of the (n + 1)th first circuit stage, and the second connection terminal of the nth first circuit stage is electrically connected to the first connection terminal of the (n + 1)th first circuit stage. The second circuit stage includes a third switch and a fourth switch, and has a third connection terminal and a fourth connection terminal. The first end and the second end of the third switch are respectively electrically connected to the second end of the first switch of the Nth first circuit stage and the third connection terminal, and the first end and the second end of the fourth switch are respectively electrically connected to the second end of the second switch of the Nth first circuit stage and the fourth connection terminal. The third connection terminal is electrically connected to the second connection terminal of the Nth first circuit stage, and the fourth connection terminal is electrically connected to the first connection terminal of the Nth first circuit stage. The third circuit stage includes a first inductor, a second inductor, a first rectifying unit, and a second rectifying unit. The first inductor and the second inductor are magnetically coupled to each other, where the first inductor is electrically connected between the second end of the third switch of the second circuit stage and the output positive terminal, and the second inductor is electrically connected between the second end of the fourth switch of the second circuit stage and the output positive terminal. The first rectifying unit is electrically connected between the second end of the third switch of the second circuit stage and the output negative terminal, and the second rectifying unit is electrically connected between the second end of the fourth switch of the second circuit stage and the output negative terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Schematic diagram of the circuit structure of the power conversion device according to the first embodiment of the present case.

[0009] Figure 2 For Figure 1 Schematic diagram of the main working waveforms of the power conversion device.

[0010] Figure 3A Illustrate Figure 1 The switching states of the power conversion device when operating in the first mode.

[0011] Figure 3B Illustrate Figure 1 The first operating mode formed when the power conversion device shown in Figure 1 operates in the first mode.

[0012] Figure 4A Illustrate Figure 1 The switching state of the power conversion device shown in Figure 1 when it operates in the second mode.

[0013] Figure 4B Illustrate Figure 1 The second operating mode formed when the power conversion device shown in Figure 1 operates in the second mode.

[0014] Figure 5 Schematic diagram of the circuit structure of the power conversion device according to the second embodiment of this case.

[0015] Figure 6A Illustrate Figure 5 The switching state of the power conversion device shown in Figure 5 when it operates in the first mode.

[0016] Figure 6B Illustrate Figure 5 The first operating mode formed when the power conversion device shown in Figure 5 operates in the first mode.

[0017] Figure 7A Illustrate Figure 5 The switching state of the power conversion device shown in Figure 5 when it operates in the second mode.

[0018] Figure 7B Illustrate Figure 5 The second operating mode formed when the power conversion device shown in Figure 5 operates in the second mode.

[0019] Figure 8 Schematic diagram of the circuit structure of the general power conversion device in an embodiment of this case, where the power conversion device includes N first circuit stages and N is an odd number.

[0020] Figure 9 Illustrate Figure 8 The first operating mode formed when the power conversion device shown in Figure 8 operates in the first mode.

[0021] Figure 10 Illustrate Figure 8 The second operating mode formed when the power conversion device shown in Figure 8 operates in the second mode.

[0022] Figure 11 Schematic diagram of the circuit structure of the general power conversion device in an embodiment of this case, where the power conversion device includes N first circuit stages and N is an even number.

[0023] Figure 12 Illustrate Figure 11The first operating mode formed when the power conversion device operates in the first mode.

[0024] Figure 13 Illustrates Figure 11 The second operating mode formed when the power conversion device operates in the second mode.

[0025] Figure 14 Schematic diagram of the circuit structure of the power conversion device according to the third embodiment of this case.

[0026] Figure 15 Is Figure 14 Schematic diagram of the main operating waveforms of the power conversion device.

[0027] Figure 16 Illustrates Figure 14 The first operating mode formed when the power conversion device operates in the first mode.

[0028] Figure 17 Illustrates Figure 14 The second operating mode formed when the power conversion device operates in the second mode.

[0029] Figure 18 Illustrates Figure 8 The first operating mode of the general power conversion device in [Case] when N = 3 and each energy storage element includes a capacitor and an auxiliary inductor.

[0030] Figure 19 Illustrates Figure 8 The first operating mode of the general power conversion device in [Case] when each energy storage element includes a capacitor and an auxiliary inductor.

[0031] Figure 20 Schematic diagram of the circuit structure of the power conversion device according to the fourth embodiment of this case.

[0032] Figure 21 Is Figure 20 Schematic diagram of the main operating waveforms of the power conversion device.

[0033] Figure 22 Illustrates Figure 20 The first operating mode formed when the power conversion device operates in the first mode.

[0034] Figure 23 Illustrates Figure 20 The second operating mode formed when the power conversion device operates in the second mode.

[0035] Figure 24 Illustrates Figure 8 The first operating mode of the general power conversion device in [Case] when N = 5 and the energy storage elements of the odd-numbered first circuit stages include capacitors and auxiliary inductors.

[0036] Figure 25 Illustrate Figure 8 The first operating mode of the general power conversion device in the present invention when the energy storage element in the odd-numbered first circuit stage includes a capacitor and an auxiliary inductor.

[0037] Figure 26 Schematic diagram of the circuit structure of the power conversion device according to the fifth embodiment of the present case.

[0038] Figure 27 For Figure 26 Schematic diagram of the main operating waveforms of the power conversion device.

[0039] Figure 28 Illustrate Figure 26 The first operating mode formed by the power conversion device when operating in the first mode.

[0040] Figure 29 Illustrate Figure 26 The second operating mode formed by the power conversion device when operating in the second mode.

[0041] Figure 30 Illustrate Figure 8 The first operating mode of the general power conversion device in the present invention when N is 7 and p is 2.

[0042] Figure 31 Illustrate Figure 8 The first operating mode of the general power conversion device in the present invention when (N + 1) / p = 2.

[0043] Figure 32 Illustrate Figure 8 The first operating mode of the general power conversion device in the present invention when N is 5 and p is 1.

[0044] Figure 33 Illustrate Figure 8 The first operating mode of the general power conversion device in the present invention when including at least a pair of auxiliary inductors.

[0045] Figure 34 Illustrate Figure 8 The first operating mode of the general power conversion device in the present invention when N is 3 and only includes one auxiliary inductor.

[0046] Figure 35 Illustrate Figure 8 The first operating mode of the general power conversion device in the present invention when only includes one auxiliary inductor.

[0047] Figure 36 Schematic diagram of the circuit structure of the power conversion device according to the sixth embodiment of the present case.

[0048] Figure 37Illustrates Figure 36 The first operating mode formed when the power conversion device works in the first mode.

[0049] Figure 38 Illustrates Figure 36 The second operating mode formed when the power conversion device works in the second mode.

[0050] Figure 39 It is a schematic diagram of the circuit structure of the power conversion device according to the seventh embodiment of this case.

[0051] Among them, the reference numerals are explained as follows:

[0052] 1a: Power conversion device

[0053] Vin+: Positive input terminal

[0054] Vin-: Negative input terminal

[0055] Vo+: Positive output terminal

[0056] Vo-: Negative output terminal

[0057] L1: First inductor

[0058] L2: Second inductor

[0059] Vin: Input voltage

[0060] Vo: Output voltage

[0061] S11, S12, S13: First switch

[0062] S21, S22, S23: Second switch

[0063] S3: Third switch

[0064] S4: Fourth switch

[0065] C11, C12, C13: First capacitor

[0066] C21, C22, C23: Second capacitor

[0067] P11, P12, P13, P14: First connection terminal

[0068] P21, P22, P23, P24: Second connection terminal

[0069] P3: Third connection terminal

[0070] P4: Fourth connection terminal

[0071] Lr1: First resonant inductor

[0072] Lr2: Second resonant inductor

[0073] SR1: First rectifying switch

[0074] SR2: Second rectifying switch

[0075] Cin: Input capacitor

[0076] Co: Output capacitor

[0077] Io1, Io2: Currents

[0078] VL2: Voltage

[0079] VC11, VC12, VC13, VC21, VC22, VC23: Voltages

[0080] t: Time

[0081] t0, t1, t2, t3, t4: Moments

[0082] 1b: Power conversion device

[0083] 1: Power conversion device

[0084] C1n, C1N: First capacitor

[0085] C2n, C2N: Second capacitor

[0086] S1n, S1(n + 1), S1N: First switch

[0087] P1n, P1(n + 1), P1N: First connection terminal

[0088] S2n, S2(n + 1), S2N: Second switch

[0089] P2n, P2(n + 1), P2N: Second connection terminal

[0090] S1x, S1y: First switch

[0091] S2x, S2y: Second switch

[0092] C1(N - 1), C1j, C1(j + 1), C1i, C1(i + 1): First capacitor

[0093] C2(N - 1), C2i, C2(i + 1), C2j, C2(j + 1): Second capacitor

[0094] 1c: Power conversion device

[0095] L11, L21, L12, L22: Auxiliary inductors

[0096] Lr11, Lr21, Lr12, Lr22: Resonant inductors

[0097] ILr11, ILr21, ILr12, ILr22: Current

[0098] VL1, VL11, VL21, VL12, VL22: Voltage

[0099] L13, L23: Auxiliary inductance

[0100] Lr13, Lr23: Resonant inductance

[0101] L2i, L2(i + 1), L1j, L1(j + 1), L2N, L1N, L1(N - 1): Auxiliary inductance

[0102] Lr2N, Lr1N, Lr1(N - 1): Resonant inductance

[0103] 1d: Power conversion device

[0104] VL13, VL23: Voltage

[0105] ILr13, ILr23: Current

[0106] C14, C15: First capacitor

[0107] C24, C25, C2(N - 2): Second capacitor

[0108] L15, L25, L2(N - 2): Auxiliary inductance

[0109] Lr15, Lr25, Lr2(N - 2): Resonant inductance

[0110] 1e: Power conversion device

[0111] L31, L41, L32, L42: Auxiliary inductance

[0112] Lr31, Lr41, Lr32, Lr42: Resonant inductance

[0113] VL31, VL41: Voltage

[0114] ILr31, ILr41: Current

[0115] C16, C17: First capacitor

[0116] C26, C27: Second capacitor

[0117] L3p, L4p: Auxiliary inductance

[0118] Lr3p, Lr4p: Resonant inductance

[0119] C1(N - 2), C1(N - 3): First capacitor

[0120] C1(k - 1), C1(k - 2), C1(N - k + 1), C1(N - k + 2): First capacitor

[0121] C2k, C2(k - 1), C2(N - k + 2), C2(N - k + 3): Second capacitor

[0122] 1f: Power conversion device

[0123] L3: Third inductor

[0124] L4: Fourth inductor

[0125] 1g: Power conversion device

[0126] T1, T2: Nodes Detailed implementation manners

[0127] Some typical embodiments embodying the features and advantages of this case will be described in detail in the following description. It should be understood that this case can have various variations in different aspects, all of which do not depart from the scope of this case.

[0128] Please refer to Figure 1 , Figure 1 which is a schematic circuit diagram of the power conversion device according to the first embodiment of this case. As Figure 1 shown, the power conversion device 1a includes an input positive terminal Vin+, an input negative terminal Vin-, an output positive terminal Vo+, an output negative terminal Vo-, three first circuit stages, a second circuit stage, and a third circuit stage. The input positive terminal Vin+ and the input negative terminal Vin- are used to receive the input voltage Vin, the output positive terminal Vo+ and the output negative terminal Vo- are used to provide the output voltage Vo, and the input negative terminal Vin- is coupled to the output negative terminal Vo-. The three first circuit stages, the second circuit stage, and the third circuit stage are cascaded in sequence between the input positive terminal Vin+ and the output negative terminal Vo-.

[0129] The first first circuit stage includes a first switch S11, a second switch S21, a first capacitor C11, and a second capacitor C21, and has a first connection end P11 and a second connection end P21. Among them, the first end and the second end of the first switch S11 are electrically connected to the input positive terminal Vin+ and the first end of the first capacitor C11 respectively, the second end of the first capacitor C11 is electrically connected to the first connection end P11, the first end and the second end of the second switch S21 are electrically connected to the input positive terminal Vin+ and the first end of the second capacitor C21 respectively, and the second end of the second capacitor C21 is electrically connected to the second connection end P21.

[0130] The second first circuit stage includes a first switch S12, a second switch S22, a first capacitor C12, and a second capacitor C22, and has a first connection terminal P12 and a second connection terminal P22. The first end of the first switch S12 is electrically connected to the second end of the first switch S11 of the first first circuit stage. The second end of the first switch S12 is electrically connected to the first end of the first capacitor C12. The second end of the first capacitor C12 is electrically connected to the first connection terminal P12. The first end of the second switch S22 is electrically connected to the second end of the second switch S21 of the first first circuit stage. The second end of the second switch S22 is electrically connected to the first end of the second capacitor C22. The second end of the second capacitor C22 is electrically connected to the second connection terminal P22.

[0131] The third first circuit stage includes a first switch S13, a second switch S23, a first capacitor C13, and a second capacitor C23, and has a first connection terminal P13 and a second connection terminal P23. The first end of the first switch S13 is electrically connected to the second end of the first switch S12 of the second first circuit stage. The second end of the first switch S13 is electrically connected to the first end of the first capacitor C13. The second end of the first capacitor C13 is electrically connected to the first connection terminal P13. The first end of the second switch S23 is electrically connected to the second end of the second switch S22 of the second first circuit stage. The second end of the second switch S23 is electrically connected to the first end of the second capacitor C23. The second end of the second capacitor C23 is electrically connected to the second connection terminal P23.

[0132] The second circuit stage includes a third switch S3 and a fourth switch S4, and has a third connection terminal P3 and a fourth connection terminal P4. The first end of the third switch S3 is electrically connected to the second end of the first switch S13 of the third first circuit stage. The second end of the third switch S3 is electrically connected to the third connection terminal P3. The first end of the fourth switch S4 is electrically connected to the second end of the second switch S23 of the third first circuit stage. The second end of the fourth switch S4 is electrically connected to the fourth connection terminal P4.

[0133] The first connection terminal P11 of the first first circuit stage, the second connection terminal P22 of the second first circuit stage, the first connection terminal P13 of the third first circuit stage, and the fourth connection terminal P4 of the second circuit stage are connected. The second connection terminal P21 of the first first circuit stage, the first connection terminal P12 of the second first circuit stage, the second connection terminal P23 of the third first circuit stage, and the third connection terminal P3 of the second circuit stage are connected. In addition, in this embodiment, the first end and the second end of the first capacitor of each first circuit stage are the positive terminal and the negative terminal respectively, and the first end and the second end of the second capacitor of each first circuit stage are the positive terminal and the negative terminal respectively.

[0134] The third circuit stage includes a first inductor L1, a second inductor L2, a first rectifying unit, and a second rectifying unit. The first inductor L1 and the second inductor L2 are electromagnetically coupled to each other to form a coupled inductor. Among them, the first inductor L1 is electrically connected between the second terminal of the third switch S3 of the second circuit stage and the positive output terminal Vo+. The second inductor L2 is electrically connected between the second terminal of the fourth switch S4 of the second circuit stage and the positive output terminal Vo+. Io1 is the current flowing through the first inductor L1, and Io2 is the current flowing through the second inductor L2. In some embodiments, the ends of the first inductor L1 connected to the positive output terminal Vo+ and the ends of the second inductor L2 connected to the positive output terminal Vo+ are of opposite polarities. The number of turns of the first inductor L1 and the second inductor L2 is not limited, and the turns ratio of the first inductor L1 and the second inductor L2 is fixed at 1. In some embodiments, the first inductor L1 and the second inductor L2 form a transformer. In addition, in some embodiments, the first capacitors and the second capacitors in all the first circuit stages are resonant capacitors and are used to resonate with the first resonant inductor Lr1 and the second resonant inductor Lr2. Among them, the first resonant inductor Lr1 can be the leakage inductance of the first inductor L1 or an independent inductor connected in series with the first inductor L1, and the second resonant inductor Lr2 can be the leakage inductance of the second inductor L2 or an independent inductor connected in series with the second inductor L2. In some embodiments, the resonant frequency at which the resonant capacitors resonate with the first resonant inductor Lr1 and the second resonant inductor Lr2 is equal to the switching frequencies of the respective first switches and second switches, thereby realizing the soft switching of the switching devices.

[0135] The first rectifying unit is electrically connected between the second terminal of the third switch S3 of the second circuit stage and the negative output terminal Vo-. The second rectifying unit is electrically connected between the second terminal of the fourth switch S4 of the second circuit stage and the negative output terminal Vo-. The first rectifying unit and the second rectifying unit can adopt an appropriate topology to achieve their rectifying functions. For example, in this embodiment, the first rectifying unit includes a first rectifying switch SR1, and the second rectifying unit includes a second rectifying switch SR2.

[0136] In some embodiments, the power conversion device 1a further includes an input capacitor Cin and an output capacitor Co. Among them, the two ends of the input capacitor Cin are respectively electrically connected to the positive input terminal Vin+ and the negative input terminal Vin-. The voltage across the input capacitor Cin is equal to the input voltage Vin. The two ends of the output capacitor Co are respectively electrically connected to the positive output terminal Vo+ and the negative output terminal Vo-. The voltage across the output capacitor Co is equal to the output voltage Vo.

[0137] Please refer to Figure 2 and match with Figure 1 , Figure 2 is Figure 1 a schematic diagram of the main operating waveforms of the power conversion device 1a. In Figure 2Among them, S11, S12, S13, S21, S22, S23, S3, S4, SR1, and SR2 respectively represent the driving signals of the first switches S11, S12, and S13, the second switches S21, S22, and S23, the third switch S3, the fourth switch S4, the first rectifying switch SR1, and the second rectifying switch SR2. VL2 is the voltage across the second inductor L2. VC11, VC12, VC13, VC21, VC22, and VC23 are the voltages across the first capacitors C11, C12, and C13 and the second capacitors C21, C22, and C23 respectively. The period from time t0 to t4 is one working cycle of the power conversion device 1a. The power conversion device 1a alternately operates in the first mode and the second mode. First, during the period from time t0 to t1, the power conversion device 1a operates in the first mode. Then, the period from time t1 to t2 is the dead time, during which all the switches in the power conversion device 1a are turned off. Next, during the period from time t2 to t3, the power conversion device 1a operates in the second mode. Finally, the period from time t3 to t4 is the dead time, during which all the switches in the power conversion device 1a are turned off. In some embodiments, in one working cycle of the power conversion device 1a, the duration of the power conversion device 1a operating in the first mode is less than or equal to half of the working cycle, and the duration of the power conversion device 1a operating in the second mode is less than or equal to half of the working cycle.

[0138] During Figure 2 the period from time t0 to t1 as shown, the power conversion device 1a operates in the first mode. In the first mode, the first switches S11 and S13, the second switch S22, the fourth switch S4, and the first rectifying switch SR1 are turned on, and the first switch S12, the second switches S21 and S23, the third switch S3, and the second rectifying switch SR2 are turned off. The corresponding switch states are shown in Figure 3A . Furthermore, when the power conversion device 1a operates in the first mode, it forms Figure 3B the first working mode as shown. As Figure 3B shown, in the first working mode, the first capacitor C11 is connected in series with the input capacitor Cin to form a capacitor branch, the second capacitors C22 and C21 are connected in series to form another capacitor branch, the first capacitors C13 and C12 are connected in series to form yet another capacitor branch, all the capacitor branches and the second capacitor C23 are connected in parallel, then connected in series with the second inductor L2, and then connected in parallel with the first inductor L1. In this embodiment, there are four equivalent capacitor branches in parallel to transfer energy to the first inductor L1 and the second inductor L2. Please refer to Figure 2 , Figure 3A and Figure 3B. In the first mode, the first capacitor C11, the second capacitor C22, and the first capacitor C13 are charged, so the corresponding voltages VC11, VC22, and VC13 rise, and the second capacitor C21, the first capacitor C12, and the second capacitor C23 are discharged, so the corresponding voltages VC21, VC12, and VC23 fall. In addition, the total capacitance after all capacitor branches are connected in parallel resonates with the first resonant inductor Lr1 and the second resonant inductor Lr2, causing the resonant current to discharge the junction capacitances of the first switch S12, the second switch S21, the second switch S23, the third switch S3, and the second rectifying switch SR2. Therefore, these switches can achieve zero-voltage turn-on when conducting subsequently (for example, in the second mode), thereby reducing switching losses and improving efficiency.

[0139] According to the first operating mode, the following relational equations can be obtained:

[0140] VC23 = Vin - VC11 = VC21 - VC22 = VC12 - VC13 (1)

[0141] Furthermore, since the first inductor L1 and the second inductor L2 are coupled and the turns ratio is 1, in terms of the average value during the first mode, the following can be obtained:

[0142] VC23 = 2Vo (2)

[0143] Please refer to Figure 2 . During the time period from t2 to t3, the power conversion device 1a operates in the second mode. In the second mode, the first switch S12, the second switch S21, the second switch S23, the third switch S3, and the second rectifying switch SR2 are turned on, and the first switch S11, the first switch S13, the second switch S22, the fourth switch S4, and the first rectifying switch SR1 are turned off. The corresponding switch states are shown in Figure 4A . Furthermore, when the power conversion device 1a operates in the second mode, it forms Figure 4B the second operating mode shown in Figure 4B . As shown in Figure 2 , Figure 4A and Figure 4B。In the second mode, the first capacitor C11, the second capacitor C22, and the first capacitor C13 discharge, so the corresponding voltages VC11, VC22, and VC13 decrease, and the second capacitor C21, the first capacitor C12, and the second capacitor C23 charge, so the corresponding voltages VC21, VC12, and VC23 increase. In addition, the total capacitance of all capacitor branches resonates with the first resonant inductor Lr1 and the second resonant inductor Lr2, causing the resonant current to discharge the junction capacitances of the first switches S11 and S13, the second switch S22, the fourth switch S4, and the first rectifying switch SR1. Therefore, when these switches conduct subsequently (e.g., in the first mode), zero-voltage conduction can be achieved to reduce switching losses and improve efficiency.

[0144] According to the second operating mode, the following relational equations can be obtained:

[0145] VC13 = Vin - VC21 = VC11 - VC12 = VC22 - VC23 (3)

[0146] Furthermore, since the first inductor L1 and the second inductor L2 are coupled and have a turns ratio of 1, in terms of the average value during the second mode, the following can be obtained:

[0147] VC13 = 2Vo (4)

[0148] Furthermore, referring to Figure 2 , the first capacitor C11 and the second capacitor C21 work symmetrically within one period, the first capacitor C12 and the second capacitor C22 work symmetrically within one period, and the first capacitor C13 and the second capacitor C23 work symmetrically within one period. Therefore, in terms of the average value of the capacitor voltages within one period, the following can be obtained:

[0149] VC11 = VC21

[0150] VC12 = VC22

[0151] VC13 = VC23 (5)

[0152] According to the foregoing equations (1) to (5), it can be deduced that Vin∶Vo = 8∶1. Further, it can be deduced that during the entire working cycle, the average values of the voltages VC11 and VC21 on the first capacitor C11 and the second capacitor C21 of the first circuit stage 1 are 3*Vin / 4, the average values of the voltages VC12 and VC22 on the first capacitor C12 and the second capacitor C22 of the second circuit stage 2 are 2*Vin / 4, and the average values of the voltages VC13 and VC23 on the first capacitor C13 and the second capacitor C23 of the third circuit stage 3 are Vin / 4. When the power conversion device 1a includes three first circuit stages, the ratio of the input voltage Vin to the output voltage Vo is 8∶1. The capacitors in the three first circuit stages store or release energy, step-down the input voltage Vin stage by stage, and then obtain the required output voltage Vo through voltage division by the coupled inductor. For example, in this embodiment, the input voltage Vin is step-down three times, and the step-down value of each first circuit stage is substantially equal, and the step-down value is basically equal to Vin / 4.

[0153] The power conversion device of the present invention can step down a high input voltage to a low intermediate voltage stage by stage, and at the same time obtain the required output voltage through inductor voltage division, realizing a high voltage conversion ratio. The duty cycle can be controlled to a value close to 50%, simplifying the control. Further, in some embodiments, at least two first circuit stages are provided, and after at least two-stage step-down, the voltage conversion ratio of the input voltage Vin to the output voltage Vo is greater than 4.

[0154] In addition, in some embodiments, during a working cycle of the power conversion device 1a, the effective value of the current Io1 flowing through the first inductor L1 is substantially equal to the effective value of the current Io2 flowing through the second inductor L2.

[0155] Please refer to Figure 5 , Figure 5 which is a schematic circuit diagram of the power conversion device of the second embodiment of this case. In Figure 5 , elements with similar functions and structures to those in Figure 1 are denoted by the same reference numerals and will not be described in detail here. However, in the embodiment shown in Figure 5 , the power conversion device 1b only includes two first circuit stages. The first ends of the third switch S3 and the fourth switch S4 of the second circuit stage are respectively electrically connected to the second ends of the first switch S12 and the second switch S22 of the second first circuit stage. Furthermore, the first connection end P11 of the first first circuit stage, the second connection end P22 of the second first circuit stage, and the third connection end P3 of the second circuit stage are connected, and the second connection end P21 of the first first circuit stage, the first connection end P12 of the second first circuit stage, and the fourth connection end P4 of the second circuit stage are connected. Similarly, the power conversion device 1b can operate switchably in the first mode and the second mode.

[0156] When the power conversion device 1b operates in the first mode, as Figure 6A shown, the first switch S11, the second switch S22, the third switch S3, and the second rectifying switch SR2 are turned on, and the first switch S12, the second switch S21, the fourth switch S4, and the first rectifying switch SR1 are turned off. When the power conversion device 1b operates in the first mode, it forms Figure 6B the first operating mode as shown. As Figure 6B shown, in the first operating mode, the first capacitor C11 is connected in series with the input capacitor Cin to form a capacitor branch, the second capacitors C22 and C21 are connected in series to form another capacitor branch, all the capacitor branches and the first capacitor C12 are connected in parallel with each other, then connected in series with the first inductor L1, and then connected in parallel with the second inductor L2. In this embodiment, there are three equivalent capacitor branches in parallel to transfer energy to the first inductor L1 and the second inductor L2. In addition, the total capacitance after all the capacitor branches are connected in parallel resonates with the first resonant inductor Lr1 and the second resonant inductor Lr2, so that the resonant current discharges the junction capacitances of the first switch S12, the second switch S21, the fourth switch S4, and the first rectifying switch SR1. Therefore, these switches can achieve zero-voltage turn-on when conducting subsequently (for example, in the second mode), so as to reduce the switching loss and improve the efficiency.

[0157] When the power conversion device 1b operates in the second mode, as Figure 7A shown, the first switch S12, the second switch S21, the fourth switch S4, and the first rectifying switch SR1 are turned on, and the first switch S11, the second switch S22, the third switch S3, and the second rectifying switch SR2 are turned off. When the power conversion device 1b operates in the second mode, it forms Figure 7B the second operating mode as shown. As Figure 7B shown, in the second operating mode, the second capacitor C21 is connected in series with the input capacitor Cin to form a capacitor branch, the first capacitors C12 and C11 are connected in series to form another capacitor branch, all the capacitor branches and the second capacitor C22 are connected in parallel with each other, then connected in series with the second inductor L2, and then connected in parallel with the first inductor L1. In this embodiment, there are three equivalent capacitor branches in parallel to transfer energy to the first inductor L1 and the second inductor L2. In addition, the total capacitance after all the capacitor branches are connected in parallel resonates with the first resonant inductor Lr1 and the second resonant inductor Lr2, so that the resonant current discharges the junction capacitances of the first switch S11, the second switch S22, the third switch S3, and the second rectifying switch SR2. Therefore, these switches can achieve zero-voltage turn-on when conducting subsequently (for example, in the first mode), so as to reduce the switching loss and improve the efficiency.

[0158] Based on the analysis methods of the first operating mode and the second operating mode in the foregoing first embodiment, it can be based on Figure 6B and Figure 7BFrom the first operating mode and the second operating mode of the power conversion device 1b shown, it can be deduced that during the entire operating cycle of the power conversion device 1b, Vin∶Vo = 6∶1 can be deduced. Further, it can be deduced that the average values of the voltages VC11 and VC21 on the first capacitor C11 and the second capacitor C21 of the first first - circuit stage are 2*Vin / 3, and the average values of the voltages VC12 and VC22 on the first capacitor C12 and the second capacitor C22 of the second first - circuit stage are Vin / 3. When the power conversion device 1b includes two first - circuit stages, the ratio of the input voltage Vin to the output voltage Vo is 6∶1. In this embodiment, the input voltage Vin is stepped down in two stages, and the voltage - step - down value of each first - circuit stage is substantially equal, and the step - down value is basically equal to Vin / 3.

[0159] The foregoing first embodiment and second embodiment respectively illustrate the implementation forms when the power conversion device includes three first - circuit stages and two first - circuit stages. However, it should be noted that the number of first - circuit stages included in the power conversion device of this case is not limited.

[0160] Figure 8 It is a schematic circuit diagram of a general power conversion device in an embodiment of this case. In Figure 8 Among them, elements with similar functions and structures to those in Figure 1 are denoted by the same reference numerals, and will not be described in detail here. As Figure 8 shown, the power conversion device 1 includes N first - circuit stages, where N is an integer greater than or equal to 2. The power conversion device 1a of the foregoing first embodiment is the implementation form of the power conversion device 1 when N is equal to 3, and the power conversion device 1b of the foregoing second embodiment is the implementation form of the power conversion device 1 when N is equal to 2.

[0161] In the power conversion device 1, each first circuit stage includes a pair of switches (such as a first switch and a second switch) electrically connected and a pair of energy storage elements (such as a first capacitor and a second capacitor), and has a first connection end and a second connection end, wherein the pair of switches conduct complementarily, the pair of energy storage elements have opposite operating states, and the energy storage elements are used to divide the input voltage Vin. The first ends of the first switch S11 and the second switch S21 of the first first circuit stage are both electrically connected to the input positive terminal Vin+. In any first circuit stage, the first end and the second end of the first capacitor are respectively electrically connected to the second end of the first switch and the first connection end, and the first end and the second end of the second capacitor are respectively electrically connected to the second end of the second switch and the second connection end. The second end of the first switch S1n of the nth first circuit stage is also electrically connected to the first end of the first switch S1(n + 1) of the (n + 1)th first circuit stage, and the second end of the second switch S2n of the nth first circuit stage is also electrically connected to the first end of the second switch S2(n + 1) of the (n + 1)th first circuit stage, where n is a positive integer less than N. In addition, the first connection end P1n of the nth first circuit stage is electrically connected to the second connection end P2(n + 1) of the (n + 1)th first circuit stage, and the second connection end P2n of the nth first circuit stage is electrically connected to the first connection end P1(n + 1) of the (n + 1)th first circuit stage. It can be seen from this that among the N first circuit stages, the N first switches S11 - S1N are connected in series in sequence, and the N second switches S21 - S2N are connected in series in sequence; in each first circuit stage, the first switch and the first energy storage element are electrically connected to a node, the second switch and the second energy storage element are electrically connected to another node, and the first energy storage element is electrically connected to the second energy storage element of the adjacent first circuit stage.

[0162] The second circuit stage includes a pair of switches (such as a third switch S3 and a fourth switch S4) that conduct complementarily and has a third connection end P3 and a fourth connection end P4. The first end and the second end of the third switch S3 are respectively electrically connected to the second end of the first switch S1N of the Nth first circuit stage and the third connection end P3, and the first end and the second end of the fourth switch S4 are respectively electrically connected to the second end of the second switch S2N of the Nth first circuit stage and the fourth connection end P4. The third connection end P3 is electrically connected to the second connection end P2N of the Nth first circuit stage, and the fourth connection end P4 is electrically connected to the first connection end P1N of the Nth first circuit stage.

[0163] The third circuit stage includes a pair of switches (such as a first rectifying switch SR1 of the first rectifying unit and a second rectifying switch SR2 of the second rectifying unit) electrically connected and a magnetic element (such as a first inductor L1 and a second inductor L2).

[0164] When the power conversion device 1 operates in the first mode, the first switch S1x of the x-th first circuit stage is turned on, the second switch S2x of the x-th first circuit stage is turned off, the first switch S1y of the y-th first circuit stage is turned off, and the second switch S2y of the y-th first circuit stage is turned on, where x is an odd number greater than zero and less than or equal to N, and y is an even number greater than 1 and less than or equal to N. When the power conversion device 1 operates in the second mode, the first switch S1x of the x-th first circuit stage is turned off, the second switch S2x of the x-th first circuit stage is turned on, the first switch S1y of the y-th first circuit stage is turned on, and the second switch S2y of the y-th first circuit stage is turned off. In short, in the first mode, the first switch and the second switch of the odd-numbered first circuit stages are turned on and off respectively, and the first switch and the second switch of the even-numbered first circuit stages are turned off and on respectively; in the second mode, the switching states of all switches are opposite to those in the first mode.

[0165] It should be noted that the connection relationship between the first connection terminal P1N and the second connection terminal P2N of the N-th first circuit stage and the first connection terminal P11 and the second connection terminal P21 of the first first circuit stage will be different depending on whether N is odd or even. This difference will result in different control methods for the third switch S3 and the fourth switch S4 in the second circuit stage and the first rectifying switch SR1 and the second rectifying switch SR2 in the third circuit stage, and will also make the first operating mode and the second operating mode different. For the sake of understanding, the control methods of the rectifying switches and the operating modes when N takes different values will be described below.

[0166] In Figure 8 In the illustrated embodiment, N is odd. When N is odd, the first connection terminal P1N of the N-th first circuit stage is electrically connected to the first connection terminal P11 of the first first circuit stage, and the second connection terminal P2N of the N-th first circuit stage is electrically connected to the second connection terminal P21 of the first first circuit stage. When the power conversion device 1 operates in the first mode, the first switch and the second switch of the odd-numbered first circuit stages are turned on and off respectively, the first switch and the second switch of the even-numbered first circuit stages are turned off and on respectively, the third switch S3 is turned off, the fourth switch S4 is turned on, the first rectifying switch SR1 is turned on, and the second rectifying switch SR2 is turned off. When the power conversion device 1 operates in the second mode, the first switch and the second switch of the odd-numbered first circuit stages are turned off and on respectively, the first switch and the second switch of the even-numbered first circuit stages are turned on and off respectively, the third switch S3 is turned on, the fourth switch S4 is turned off, the first rectifying switch SR1 is turned off, and the second rectifying switch SR2 is turned on.

[0167] When N is odd, in the first operating mode, as Figure 9As shown, the first capacitor C11 of the first first circuit stage is connected in series with the input capacitor Cin to form a capacitor branch. The second capacitor C2i of the i-th first circuit stage is connected in series with the second capacitor C2(i + 1) of the (i + 1)-th first circuit stage to form another capacitor branch. The first capacitor C1j of the j-th first circuit stage is connected in series with the first capacitor C1(j + 1) of the (j + 1)-th first circuit stage to form yet another capacitor branch, where i is an odd number greater than zero and less than N, and j is an even number greater than 1 and less than N. All the capacitor branches and the second capacitor C2N of the N-th first circuit stage are connected in parallel with each other, then connected in series with the second inductor L2, and then connected in parallel with the first inductor L1. The first end of the first inductor L1 is connected to the second inductor L2 and the positive output terminal Vo+, and the second end of the first inductor L1 is connected to the negative output terminal Vo-. There are N + 1 equivalent capacitor branches connected in parallel to transfer energy to the first inductor L1 and the second inductor L2.

[0168] When N is an odd number, in the second operating mode, as Figure 10 shown, the second capacitor C21 of the first first circuit stage is connected in series with the input capacitor Cin to form a capacitor branch. The first capacitor C1i of the i-th first circuit stage is connected in series with the first capacitor C1(i + 1) of the (i + 1)-th first circuit stage to form another capacitor branch. The second capacitor C2j of the j-th first circuit stage is connected in series with the second capacitor C2(j + 1) of the (j + 1)-th first circuit stage to form yet another capacitor branch. All the capacitor branches and the first capacitor C1N of the N-th first circuit stage are connected in parallel with each other, then connected in series with the first inductor L1, and then connected in parallel with the second inductor L2. The first end of the second inductor L2 is connected to the first inductor L1 and the positive output terminal Vo+, and the second end of the second inductor L2 is connected to the negative output terminal Vo-. There are N + 1 equivalent capacitor branches connected in parallel to transfer energy to the first inductor and the second inductor.

[0169] Figure 11 It is a schematic circuit diagram of the general power conversion device 1 in an embodiment of this case when N is an even number. In Figure 11 it is the same as Figure 1 , Figure 5 and Figure 8Elements with similar functions and structures in the [text] are denoted by the same reference numerals and will not be elaborated here. When N is an even number, the first connection terminal P1N of the Nth first circuit stage is electrically connected to the second connection terminal P21 of the first first circuit stage, and the second connection terminal P2N of the Nth first circuit stage is electrically connected to the first connection terminal P11 of the first first circuit stage. When the power conversion device 1 operates in the first mode, the first switch and the second switch of the odd-numbered first circuit stages are turned on and off respectively, the first switch and the second switch of the even-numbered first circuit stages are turned off and on respectively, the third switch S3 is turned on, the fourth switch S4 is turned off, the first rectifier switch SR1 is turned off, and the second rectifier switch SR2 is turned on. When the power conversion device 1 operates in the second mode, the first switch and the second switch of the odd-numbered first circuit stages are turned off and on respectively, the first switch and the second switch of the even-numbered first circuit stages are turned on and off respectively, the third switch S3 is turned off, the fourth switch S4 is turned on, the first rectifier switch SR1 is turned on, and the second rectifier switch SR2 is turned off.

[0170] When N is an even number, in the first operating mode, as Figure 12 shown, the first capacitor C11 of the first first circuit stage is connected in series with the input capacitor Cin to form a capacitor branch, and the second capacitor C2i of the ith first circuit stage is connected in series with the second capacitor C2(i + 1) of the (i + 1)th first circuit stage to form another capacitor branch, where i is an odd number greater than zero and less than N. If N is greater than 3, the first capacitor C1j of the jth first circuit stage is connected in series with the first capacitor C1(j + 1) of the (j + 1)th first circuit stage to form yet another capacitor branch, where j is an even number greater than 1 and less than N. All the capacitor branches and the first capacitor C1N of the Nth first circuit stage are connected in parallel with each other, then connected in series with the first inductor L1, and then connected in parallel with the second inductor L2. The first end of the second inductor L2 is connected to the first inductor L1 and the positive output terminal Vo+, and the second end of the second inductor L2 is connected to the negative output terminal Vo-. There are N + 1 equivalent capacitor branches in parallel to transfer energy to the first inductor L1 and the second inductor L2.

[0171] When N is an even number, in the second operating mode, as Figure 13As shown, the second capacitor C21 of the first first circuit stage is connected in series with the input capacitor Cin to form a capacitive branch, and the first capacitor C1i of the i-th first circuit stage is connected in series with the first capacitor C1(i + 1) of the (i + 1)-th first circuit stage to form another capacitive branch. If N is greater than 3, the second capacitor C2j of the j-th first circuit stage is connected in series with the second capacitor C2(j + 1) of the (j + 1)-th first circuit stage to form yet another capacitive branch. All capacitive branches and the second capacitor C2N of the N-th first circuit stage are connected in parallel with each other, then connected in series with the second inductor L2, and then connected in parallel with the first inductor L1. The first end of the first inductor L1 is connected to the second inductor L2 and the positive output terminal Vo+, and the second end of the first inductor L1 is connected to the negative output terminal Vo-. There are N + 1 equivalent capacitive branches in parallel to transfer energy to the first inductor L1 and the second inductor L2.

[0172] As can be seen from the foregoing, within one switching period, a pair of switches in each of the N first circuit stages, the second circuit stage, and the third circuit stage includes a first-phase switch (e.g., Figure 11 the first switch of the odd-numbered first circuit stages, the second switch of the even-numbered first circuit stages, the third switch S3, and the second rectifying switch SR2 in Figure 11 ), and a second-phase switch (e.g.,

[0173] Furthermore, when the first-phase switch or the second-phase switch is turned on, there are at least three branches for transferring energy to the magnetic element of the third circuit stage, and each branch includes at least one energy storage element. Specifically, when the first-phase switch is turned on, the first-phase energy storage element of the first first circuit stage and the input capacitor Cin are connected in series to form the first branch, the second-phase energy storage element of the nth first circuit stage and the first-phase energy storage element of the (n + 1)th first circuit stage are connected in series to form the (n + 1)th branch, and the second-phase energy storage element of the Nth first circuit stage forms the (N + 1)th branch. All N + 1 branches are connected in parallel to transfer energy to the magnetic element of the third circuit stage. Similarly, when the second-phase switch is turned on, the second-phase energy storage element of the first first circuit stage and the input capacitor Cin are connected in series to form the first branch, the first-phase energy storage element of the nth first circuit stage and the second-phase energy storage element of the (n + 1)th first circuit stage are connected in series to form the (n + 1)th branch, and the first-phase energy storage element of the Nth first circuit stage forms the (N + 1)th branch. All N + 1 branches are connected in parallel to transfer energy to the magnetic element of the third circuit stage.

[0174] In addition, regardless of whether N is odd or even, when the power conversion device 1 operates in the first mode or the second mode, the total capacitance of all capacitor branches in the corresponding operating mode resonates with the first resonant inductor Lr1 and the second resonant inductor Lr2, so that the resonant current discharges the junction capacitance of all switches in the off state. Therefore, these switches can achieve zero-voltage turn-on when conducting subsequently, thereby reducing switch losses and improving efficiency.

[0175] Furthermore, by analyzing the first operating mode and the second operating mode in the foregoing embodiments, it can be deduced that during the entire operating cycle of the power conversion device 1, it can be deduced that Vin∶Vo = 2(N + 1)∶1. Further, it can be deduced that the average value of the voltages on the first capacitor C1n and the second capacitor C2n of the nth first circuit stage (i.e., the average value of the voltage on any energy storage element) is (N + 1 - n)*Vin / (N + 1). In the power conversion device 1 including N first circuit stages, the ratio of the input voltage Vin to the output voltage Vo is 2(N + 1)∶1. The capacitors in the N first circuit stages store or release energy, step-down the input voltage Vin level by level, and then obtain the required output voltage Vo through the voltage division of the coupled inductor. For example, in this embodiment, the input voltage Vin is stepped down N times, and the stepped-down value of each first circuit stage is substantially equal, and the stepped-down value is basically equal to Vin / (N + 1). As can be seen from the foregoing, in the power conversion device 1 of this case, the corresponding number of first circuit stages can be set according to actual needs to achieve the required input-output voltage ratio, so it has better applicability and can be applied to applications with high input-output voltage ratio and high power density requirements. In addition, all switches of the power conversion device 1 can achieve soft switching, so the switch losses can be reduced and the overall efficiency of the power conversion device can be improved.

[0176] In addition, in some embodiments, the input positive terminal Vin+, the input negative terminal Vin-, the output positive terminal Vo+, the output negative terminal Vo-, the N first circuit stages, the second circuit stage, and the third circuit stage form a power conversion module, and the power conversion device may include a plurality of power conversion modules, and the plurality of power modules may operate in parallel or independently. For example, the plurality of input positive terminals Vin+ of the plurality of power conversion modules are connected, the plurality of input negative terminals Vin- of the plurality of power conversion modules are connected, the plurality of output positive terminals Vo+ of the plurality of power conversion modules are connected, and the plurality of output negative terminals Vo- of the plurality of power conversion modules are connected.

[0177] In addition, in the foregoing embodiments, the energy storage elements in the first circuit stage are all taken as capacitors as an example. However, it should be noted that the present case is not limited thereto. For example, the energy storage elements may also include capacitors and inductors, and different energy storage elements may adopt different implementation manners. This will be described in detail below.

[0178] Please refer to Figure 14 。 Figure 14 FIG. is a schematic circuit diagram of the power conversion device according to the third embodiment of the present case. In Figure 14 Among them, elements having similar functions and structures to those in Figure 5 are denoted by the same reference numerals and will not be described herein again. However, in Figure 14In the power conversion device 1c of the illustrated embodiment, the energy storage elements of each first circuit stage include a capacitor and an auxiliary inductor. Specifically, in the first first circuit stage, one of the energy storage elements includes a first capacitor C11 and an auxiliary inductor L11, and the other energy storage element includes a second capacitor C21 and an auxiliary inductor L21, where the auxiliary inductor L11 is electrically connected between the second terminal of the first capacitor C11 and the first connection terminal P11, and the auxiliary inductor L21 is electrically connected between the second terminal of the second capacitor C21 and the second connection terminal P21. Similarly, in the second first circuit stage, one of the energy storage elements includes a first capacitor C12 and an auxiliary inductor L12, and the other energy storage element includes a second capacitor C22 and an auxiliary inductor L22, where the auxiliary inductor L12 is electrically connected between the second terminal of the first capacitor C12 and the first connection terminal P12, and the auxiliary inductor L22 is electrically connected between the second terminal of the second capacitor C22 and the second connection terminal P22. In some embodiments, the first first circuit stage further includes resonance inductors Lr11 and Lr21, where the resonance inductor Lr11 can be the leakage inductance of the auxiliary inductor L11 or an independent inductor connected in series with the auxiliary inductor L11, and the resonance inductor Lr21 can be the leakage inductance of the auxiliary inductor L21 or an independent inductor connected in series with the auxiliary inductor L21. In some embodiments, the second first circuit stage further includes resonance inductors Lr12 and Lr22, where the resonance inductor Lr12 can be the leakage inductance of the auxiliary inductor L12 or an independent inductor connected in series with the auxiliary inductor L12, and the resonance inductor Lr22 can be the leakage inductance of the auxiliary inductor L22 or an independent inductor connected in series with the auxiliary inductor L22.

[0179] Please refer to Figure 15 and in conjunction with Figure 14 , Figure 15 is Figure 14 a schematic diagram of the main working waveforms of the power conversion device 1c. In Figure 15 , VL1 is the voltage across the first inductor L1, VL2 is the voltage across the second inductor L2, VL11, VL21, VL12, and VL22 are the voltages across the auxiliary inductors L11, L21, L12, and L22 respectively, and ILr11, ILr21, ILr12, and ILr22 are the currents flowing through the resonance inductors Lr11, Lr21, Lr12, and Lr22 respectively. The switching control method of the power conversion device 1c in the first mode and the second mode is the same as that of the Figure 5 illustrated embodiment, so it will not be elaborated here.

[0180] When the power conversion device 1c operates in the first mode, it forms Figure 16 the first working mode shown. As Figure 16As shown, in the first operating mode, the auxiliary inductor L11, the first capacitor C11, and the input capacitor Cin are connected in series to form a first branch, the auxiliary inductor L22, the second capacitors C22 and C21, and the auxiliary inductor L21 are connected in series to form a second branch, and the first capacitor C12 and the auxiliary inductor L12 are connected in series to form a third branch. The first branch, the second branch, and the third branch are connected in parallel with each other, then connected in series with the first inductor L1, and then connected in parallel with the second inductor L2. In this embodiment, there are three equivalent branches in parallel to transfer energy to the first inductor L1 and the second inductor L2.

[0181] Assume that the number of turns of the windings of the auxiliary inductors L11, L21, L12, and L22 is equal, the number of turns of the windings of the first inductor L1 and the second inductor L2 is equal, and the turns ratio of the auxiliary inductor to the first or second inductor is Z∶1. According to the first operating mode, the following relational equations can be obtained:

[0182] (2 + Z)*Vo = Vin - VC11

[0183] (2 + 2Z)*Vo = VC21 - VC22

[0184] (2 + Z)*Vo = VC12 (6)

[0185] When the power conversion device 1c operates in the second mode, it forms Figure 17 the second operating mode as shown. As Figure 17 shown, in the second operating mode, the auxiliary inductor L21, the second capacitor C21, and the input capacitor Cin are connected in series to form a first branch, the auxiliary inductor L12, the first capacitors C12 and C11, and the auxiliary inductor L11 are connected in series to form a second branch, and the second capacitor C22 and the auxiliary inductor L22 are connected in series to form a third branch. The first branch, the second branch, and the third branch are connected in parallel with each other, then connected in series with the second inductor L2, and then connected in parallel with the first inductor L1. In this embodiment, there are three equivalent branches in parallel to transfer energy to the first inductor L1 and the second inductor L2.

[0186] According to the second operating mode, the following relational equations can be obtained:

[0187] (2 + Z)*Vo = Vin - VC21

[0188] (2 + 2Z)*Vo = VC11 - VC12

[0189] (2 + Z)*Vo = VC22 (7)

[0190] Furthermore, referring to Figure 15, within one cycle, the first capacitor C11 and the second capacitor C21 work symmetrically, and the first capacitor C12 and the second capacitor C22 work symmetrically. Therefore, in terms of the average value of the capacitor voltage within one cycle, we can obtain:

[0191] VC11 = VC21

[0192] VC12 = VC22 (8)

[0193] According to equations (6), (7), and (8), it can be deduced that within the entire working cycle, the ratio of the input voltage Vin to the output voltage Vo is (6 + 4Z)∶1. Furthermore, it can be deduced that the average values of the voltages VC11 and VC21 on the first capacitor C11 and the second capacitor C21 of the first first - circuit stage are (4 + 3Z)*Vin / (6 + 4Z), and the average values of the voltages VC12 and VC22 on the first capacitor C12 and the second capacitor C22 of the second first - circuit stage are (2 + Z)*Vin / (6 + 4Z). The capacitors in the two first - circuit stages store or release energy, step - down the input voltage Vin stage by stage, and an auxiliary inductor connected in series with the capacitor is added to achieve flexible voltage regulation. For example, in this embodiment, the input voltage Vin is stepped down in two stages, and at the same time, the auxiliary winding in each stage adjusts the step - down value. By adding an auxiliary winding, a flexible voltage conversion ratio can be set, where Z can be any positive number, such as 0.5, 1, ….

[0194] According to Figure 14 、 Figure 16 and Figure 17 the circuit topology of the power conversion device 1c and its first and second working modes in the first mode and the second mode, and referring to Figure 8 the general power conversion device when N is odd shown in Figure 14 it can be deduced that when N is 3 (i.e., including three first - circuit stages) and each energy - storage element includes a capacitor and an auxiliary inductor, the circuit topology of the power conversion device and its first and second working modes. In this embodiment, the topologies of the first and second first - circuit stages are similar to those in Figure 14 ; in the third first - circuit stage, one energy - storage element includes a first capacitor C13 and an auxiliary inductor L13, and the other energy - storage element includes a second capacitor C23 and an auxiliary inductor L23, where the auxiliary inductor L13 is electrically connected between the second end of the first capacitor C13 and the first connection end P13, and the auxiliary inductor L23 is electrically connected between the second end of the second capacitor C23 and the second connection end P23. In some embodiments, the third first - circuit stage further includes resonant inductors Lr13 and Lr23, where the resonant inductor Lr13 can be the leakage inductance of the auxiliary inductor L13 or an independent inductor connected in series with the auxiliary inductor L13, and the resonant inductor Lr23 can be the leakage inductance of the auxiliary inductor L23 or an independent inductor connected in series with the auxiliary inductor L23.

[0195] The corresponding first working mode is as follows Figure 18 shown. Among them, the auxiliary inductor L11, the first capacitor C11, and the input capacitor Cin are connected in series to form a first branch; the auxiliary inductors L22 and L21, and the second capacitors C22 and C21 are connected in series to form a second branch; the auxiliary inductors L13 and L12, and the first capacitors C13 and C12 are connected in series to form a third branch; the auxiliary inductor L23 and the second capacitor C23 are connected in series to form a fourth branch. The first branch, the second branch, the third branch, and the fourth branch are connected in parallel with each other, then connected in series with the second inductor L2, and then connected in parallel with the first inductor L1. In this embodiment, there are four equivalent branches in parallel to transfer energy to the first inductor L1 and the second inductor L2..

[0196] The corresponding second working mode can be deduced in the same way, so it will not be elaborated here. From the first and second working modes, it can be deduced that when the power conversion device in this case includes three first circuit stages and each energy storage element includes a capacitor and an auxiliary inductor, during the entire working cycle, the ratio of the input voltage Vin to the output voltage Vo is (8 + 6Z)∶1.

[0197] According to Figures 14 to 18 the circuit topology of the power conversion device shown and its first and second working modes in the first mode and the second mode, and referring to Figure 8 and Figure 11 the general power conversion device shown when N is odd and even, the circuit topology of the general power conversion device and its first and second working modes can be deduced when each energy storage element in each first circuit stage includes a capacitor and an auxiliary inductor.

[0198] Taking N being odd as an example, the corresponding first working mode is as follows Figure 19 shown. Among them, the first capacitor C11 and the auxiliary inductor L11 of the first first circuit stage are connected in series with the input capacitor Cin to form a first branch; the second capacitor C2i and the auxiliary inductor L2i of the i-th first circuit stage are connected in series with the second capacitor C2(i + 1) and the auxiliary inductor L2(i + 1) of the (i + 1)-th first circuit stage to form the (i + 1)-th branch; the first capacitor C1j and the auxiliary inductor L1j of the j-th first circuit stage are connected in series with the first capacitor C1(j + 1) and the auxiliary inductor L1(j + 1) of the (j + 1)-th first circuit stage to form the (j + 1)-th branch; the second capacitor C2N and the auxiliary inductor L2N of the N-th first circuit stage are connected in series to form the (N + 1)-th branch. The first branch, the second branch... the (N + 1)-th branch are connected in parallel with each other, then connected in series with the second inductor L2, and then connected in parallel with the first inductor L1. There are N + 1 equivalent branches in parallel to transfer energy to the first inductor L1 and the second inductor L2.

[0199] The corresponding second operating mode can be derived in the same way. In addition, the first and second operating modes when N is even can also be derived in the same way, so they will not be elaborated here. Based on this, it can be deduced that when each energy storage element in the general power conversion device of this case includes a capacitor and an auxiliary inductor, the ratio of the input voltage Vin to the output voltage Vo is [2(Z + 2) + (N - 1)(2Z + 2)]:1 during the entire operating cycle.

[0200] Please refer to Figure 20 . Figure 20 FIG. is a schematic circuit diagram of the power conversion device according to the fourth embodiment of this case. In Figure 20 , elements with similar functions and structures to those in Figure 1 and Figure 14 are denoted by the same reference numerals and will not be elaborated here. However, in the power conversion device 1d of the embodiment shown in Figure 20 , some energy storage elements of the first circuit stage include a capacitor and an auxiliary inductor. For example, the odd or even numbered energy storage elements of the first circuit stage include a capacitor and an auxiliary inductor, and the remaining energy storage elements of the first circuit stage include a capacitor. Specifically, in the embodiment shown in Figure 20 , the energy storage elements in the 1st and 3rd first circuit stages include capacitors (C11, C21, C13, C23) and auxiliary inductors (L11, L21, L13, L23), and the energy storage elements in the 2nd first circuit stage include capacitors (C12, C22).

[0201] Please refer to Figure 21 and in conjunction with Figure 20 , Figure 21 is a schematic diagram of the main operating waveforms of the power conversion device 1d of Figure 20 . In Figure 21 , VL13 and VL23 are the voltages across the auxiliary inductors L13 and L23 respectively, and ILr13 and ILr23 are the currents flowing through the resonant inductors Lr13 and Lr23 respectively. The switching control methods of the power conversion device 1d in the first mode and the second mode are the same as those of the embodiment shown in Figure 1 , so they will not be elaborated here.

[0202] When the power conversion device 1d operates in the first mode, it forms the first operating mode shown in Figure 22 . As shown in Figure 22As shown, in the first working mode, the auxiliary inductor L11, the first capacitor C11, and the input capacitor Cin are connected in series to form a first branch, the auxiliary inductor L13, and the first capacitors C12 and C13 are connected in series to form a second branch, the second capacitor C22, C21, and the auxiliary inductor L21 are connected in series to form a third branch, and the second capacitor C23 and the auxiliary inductor L23 are connected in series to form a fourth branch. The first branch, the second branch, the third branch, and the fourth branch are connected in parallel with each other, then connected in series with the second inductor L2, and then connected in parallel with the first inductor L1. In this embodiment, there are four equivalent branches in parallel to transfer energy to the first inductor L1 and the second inductor L2.

[0203] Assume that the number of turns of the windings of the auxiliary inductors L11, L21, L13, and L23 are equal, the number of turns of the windings of the first inductor L1 and the second inductor L2 are equal, and the turns ratio of the auxiliary inductor to the first or second inductor is Z∶1. According to the first working mode, the following relational equations can be obtained:

[0204] 2Vo = VC23 - Z*Vo

[0205] = VC21 - VC22 - Z*Vo

[0206] = VC12 - VC13 - Z*Vo

[0207] = Vin - VC11 - Z*Vo (9)

[0208] When the power conversion device 1d operates in the second mode, it forms Figure 23 the second working mode as shown. As Figure 23 shown, in the second working mode, the auxiliary inductor L21, the second capacitor C21, and the input capacitor Cin are connected in series to form a first branch, the auxiliary inductor L23, and the second capacitors C22 and C23 are connected in series to form a second branch, the first capacitor C12, C11, and the auxiliary inductor L11 are connected in series to form a third branch, and the first capacitor C13 and the auxiliary inductor L13 are connected in series to form a fourth branch. The first branch, the second branch, the third branch, and the fourth branch are connected in parallel with each other, then connected in series with the first inductor L1, and then connected in parallel with the second inductor L2. In this embodiment, there are four equivalent branches in parallel to transfer energy to the first inductor L1 and the second inductor L2.

[0209] According to the second working mode, the following relational equations can be obtained:

[0210] 2Vo = VC13 - Z*Vo

[0211] = VC11 - VC12 - Z*Vo

[0212] = VC22 - VC23 - Z*Vo

[0213] = Vin - VC21 - Z * Vo (10)

[0214] Furthermore, referring to Figure 21 , within one period, the first capacitor C11 and the second capacitor C21 work symmetrically, the first capacitor C12 and the second capacitor C22 work symmetrically, and the first capacitor C13 and the second capacitor C23 work symmetrically. Therefore, in terms of the average value of the capacitor voltages within one period, we can obtain:

[0215] VC11 = VC21

[0216] VC12 = VC22

[0217] VC13 = VC23 (11)

[0218] Based on equations (9), (10), and (11), it can be deduced that the ratio of the input voltage Vin to the output voltage Vo is (8 + 4Z)∶1. Furthermore, it can be deduced that during the entire working period, the average values of the voltages VC11 and VC21 across the first capacitor C11 and the second capacitor C21 of the first first - circuit stage are 3 * Vin / 4, the average values of the voltages VC12 and VC22 across the first capacitor C12 and the second capacitor C22 of the second first - circuit stage are Vin / 2, and the average values of the voltages VC13 and VC23 across the first capacitor C13 and the second capacitor C23 of the third first - circuit stage are Vin / 4. The three first - circuit stages step - down the input voltage Vin step by step, and the voltage step - down value of each first - circuit stage is equal, which is actually equal to Vin / 4.

[0219] According to Figure 20 , Figure 22 and Figure 23 the circuit topology of the power conversion device 1d shown in and its first and second working modes in the first mode and the second mode, and referring to Figure 8 the general power conversion device shown when N is odd, it can be deduced the circuit topology of the power conversion device when N is 5 (i.e., including five first - circuit stages) and the energy - storage elements of the odd - numbered first - circuit stages include capacitors and auxiliary inductors, and its first and second working modes. In this embodiment, the topologies of the first to third first - circuit stages are the same as Figure 20Similar to that in [description of a previous part]; in the 4th first circuit stage, the two energy storage elements include a first capacitor C14 and a second capacitor C24; in the 5th first circuit stage, one of the energy storage elements includes a first capacitor C15 and an auxiliary inductor L15, and the other energy storage element includes a second capacitor C25 and an auxiliary inductor L25. In some embodiments, the 5th first circuit stage further includes resonant inductors Lr15 and Lr25, where the resonant inductor Lr15 can be the leakage inductance of the auxiliary inductor L15 or an independent inductor connected in series with the auxiliary inductor L15, and the resonant inductor Lr25 can be the leakage inductance of the auxiliary inductor L25 or an independent inductor connected in series with the auxiliary inductor L25.

[0220] The corresponding first operating mode is as Figure 24 shown, where the auxiliary inductor L11, the first capacitor C11, and the input capacitor Cin are connected in series to form a first branch, the auxiliary inductor L21, and the second capacitors C22 and C21 are connected in series to form a second branch, the auxiliary inductor L13, and the first capacitors C13 and C12 are connected in series to form a third branch, the auxiliary inductor L23, and the second capacitors C24 and C23 are connected in series to form a fourth branch, the auxiliary inductor L15, and the first capacitors C15 and C14 are connected in series to form a fifth branch, and the auxiliary inductor L25 and the second capacitor C25 are connected in series to form a sixth branch. The first branch, the second branch, the third branch, the fourth branch, the fifth branch, and the sixth branch are connected in parallel with each other, then connected in series with the second inductor L2, and then connected in parallel with the first inductor L1. In this embodiment, there are six equivalent branches in parallel to transfer energy to the first inductor L1 and the second inductor L2.

[0221] The corresponding second operating mode can be derived in the same way, so it will not be elaborated here. From the first and second operating modes, it can be deduced that when the power conversion device of this case includes five first circuit stages, if the energy storage elements of the odd-numbered first circuit stages include capacitors and auxiliary inductors, and the energy storage elements of the even-numbered first circuit stages include capacitors, then in the entire operating cycle, the ratio of the input voltage Vin to the output voltage Vo is (12 + 6Z)∶1.

[0222] According to Figures 20 to 24 the circuit topology of the power conversion device shown and its first and second operating modes in the first and second modes, and referring to Figure 8 and Figure 11 the general power conversion device shown when N is odd and even, the circuit topology and its first and second operating modes of the general power conversion device when the energy storage elements of the odd-numbered or even-numbered first circuit stages include capacitors and auxiliary inductors can be deduced.

[0223] Taking N as an odd number and the energy storage elements of the odd-numbered first circuit stages including capacitors and auxiliary inductors as an example, the corresponding first operating mode is as Figure 25As shown, the first capacitor C11 and the auxiliary inductor L11 of the first first circuit stage are connected in series with the input capacitor Cin to form a first branch. The second capacitor C2i and the auxiliary inductor L2i of the i-th first circuit stage are connected in series with the second capacitor C2(i + 1) of the (i + 1)-th first circuit stage to form the (i + 1)-th branch. The first capacitor C1j of the j-th first circuit stage is connected in series with the first capacitor C1(j + 1) and the auxiliary inductor L1(j + 1) of the (j + 1)-th first circuit stage to form the (j + 1)-th branch. The second capacitor C2N and the auxiliary inductor L2N of the N-th first circuit stage are connected in series to form the (N + 1)-th branch. The first branch, the second branch... the (N + 1)-th branch are connected in parallel with each other, then connected in series with the second inductor L2, and then connected in parallel with the first inductor L1. There are N + 1 equivalent branches in parallel to transfer energy to the first inductor L1 and the second inductor L2.

[0224] The corresponding second operating mode can be deduced in the same way. In addition, the first and second operating modes when N is even can also be deduced in the same way, so they will not be elaborated here. Based on this, it can be deduced that when in the general power conversion device of this case, if the energy storage elements of the odd-numbered or even-numbered first circuit stages include a capacitor and an auxiliary inductor, and the energy storage elements of the remaining first circuit stages include a capacitor, then in the entire operating cycle, the ratio of the input voltage Vin to the output voltage Vo is (N + 1)*(2 + Z)∶1.

[0225] Please refer to Figure 26 . Figure 26 is a schematic circuit diagram of the power conversion device of the fifth embodiment of this case. In Figure 26 , elements with similar functions and structures to Figure 1 are denoted by the same reference numerals and will not be elaborated here. However, in the embodiment shown in Figure 26 , the power conversion device 1e further includes a pair of auxiliary inductors, one of which is shared by the first-phase energy storage elements and the other is shared by the second-phase energy storage elements. Specifically, as shown in Figure 26 , the power conversion device 1e includes auxiliary inductors L31 and L41. The auxiliary inductor L31 is electrically connected to the first capacitors C11 and C13 and the second capacitor C22. The auxiliary inductor L41 is electrically connected to the second capacitors C21 and C23 and the second capacitor C12. In this embodiment, N is equal to 3. Correspondingly, the auxiliary inductor L31 is also electrically connected to the second terminal of the fourth switch S4 of the second circuit stage, and the auxiliary inductor L41 is also electrically connected to the second terminal of the third switch S3 of the second circuit stage. In some embodiments, the power conversion device 1e further includes resonant inductors Lr31 and Lr41, where the resonant inductor Lr31 can be the leakage inductance of the auxiliary inductor L31 or an independent inductor connected in series with the auxiliary inductor L31, and the resonant inductor Lr41 can be the leakage inductance of the auxiliary inductor L41 or an independent inductor connected in series with the auxiliary inductor L41.

[0226] Please refer to Figure 27 and cooperate with Figure 26 , Figure 27 which is Figure 26 a schematic diagram of the main working waveforms of the power conversion device 1e. In Figure 27 , VL31 and VL41 are the voltages across the auxiliary inductors L31 and L41 respectively, and ILr31 and ILr41 are the currents flowing through the resonant inductors Lr31 and Lr41 respectively. The switching control methods of the power conversion device 1e in the first mode and the second mode are the same as those in the Figure 1 embodiment shown, so they will not be elaborated here.

[0227] When the power conversion device 1e operates in the first mode, it forms Figure 28 the first working mode shown. As Figure 28 shown, in the first working mode, the branch formed by the series connection of the first capacitor C11 and the input capacitor Cin is connected in parallel with the branch formed by the series connection of the first capacitors C12 and C13, and then connected in series with the auxiliary inductor L31 to form the first branch; the branch formed by the series connection of the second capacitors C22 and C21 is connected in parallel with the second capacitor C23 and then connected in series with the auxiliary inductor L41 to form the second branch. The first branch and the second branch are connected in parallel, then connected in series with the second inductor L2, and then connected in parallel with the first inductor L1. There are four equivalent capacitor circuits for transferring energy to the first inductor L1 and the second inductor L2. There are two equivalent capacitor-inductor circuits connected in parallel for transferring energy to the first inductor L1 and the second inductor L2.

[0228] Assume that the number of turns of the windings of the auxiliary inductors L31 and L41 is equal, the number of turns of the windings of the first inductor L1 and the second inductor L2 is equal, and the turns ratio of the auxiliary inductor to the first or second inductor is Z∶1. According to the first working mode, the following relational equations can be obtained:

[0229] (2 + Z)*Vo = Vin - VC11

[0230] = VC12 - VC13

[0231] = VC21 - VC22

[0232] = VC23 (12)

[0233] When the power conversion device 1e operates in the second mode, it forms Figure 29 the second working mode shown. As Figure 29As shown, in the second operating mode, the branch formed by the series connection of the second capacitor C21 and the input capacitor Cin is connected in parallel with the branch formed by the series connection of the second capacitors C22 and C23, and then connected in series with the auxiliary inductor L41 to form the first branch; the branch formed by the series connection of the first capacitors C12 and C11 is connected in parallel with the first capacitor C13 and then connected in series with the auxiliary inductor L31 to form the second branch. The first branch and the second branch are connected in parallel, then connected in series with the first inductor L1, and then connected in parallel with the second inductor L2. There are four equivalent capacitor circuits for transferring energy to the first inductor L1 and the second inductor L2. There are two equivalent capacitor-inductor circuits connected in parallel for transferring energy to the first inductor L1 and the second inductor L2.

[0234] According to the second operating mode, the following relational equations can be obtained:

[0235] (2 + Z)*Vo = Vin - VC21

[0236] = VC22 - VC23

[0237] = VC11 - VC12

[0238] = VC13 (13)

[0239] Furthermore, referring to Figure 27 , the first capacitor C11 and the second capacitor C21 work symmetrically within one period, the first capacitor C12 and the second capacitor C22 work symmetrically, and the first capacitor C13 and the second capacitor C23 work symmetrically. Therefore, in terms of the average value of the capacitor voltages within one period, it can be obtained that:

[0240] VC11 = VC21

[0241] VC12 = VC22

[0242] VC13 = VC23 (14)

[0243] Based on equations (12), (13), and (14), it can be deduced that the ratio of the input voltage Vin to the output voltage Vo is (8 + 4Z)∶1. Furthermore, it can be deduced that within the entire operating period, the average values of the voltages VC11 and VC21 on the first capacitor C11 and the second capacitor C21 of the first first circuit stage are 3*Vin / 4, the average values of the voltages VC12 and VC22 on the first capacitor C12 and the second capacitor C22 of the second first circuit stage are Vin / 2, and the average values of the voltages VC13 and VC23 on the first capacitor C13 and the second capacitor C23 of the third first circuit stage are Vin / 4. The three first circuit stages step down the voltage gradually, and the voltage reduction value of each first circuit stage is equal, which is actually equal to Vin / 4.

[0244] In the fifth embodiment, the power conversion device 1e includes only a pair of auxiliary inductors. However, the present case is not limited thereto, and the power conversion device 1e may include p pairs of auxiliary inductors, where (N + 1) / p must be an integer.

[0245] According to Figure 26 、 Figure 28 and Figure 29 the circuit topology of the power conversion device 1e shown in and its first and second operating modes in the first and second modes, and referring to Figure 8 the general power conversion device shown when N is odd, the circuit topology of the power conversion device when N is 7 (i.e., including seven first circuit stages) and p is 2 (i.e., including two pairs of auxiliary inductors) and its first and second operating modes can be obtained. In this embodiment, the first pair of auxiliary inductors of the power conversion device includes auxiliary inductors L31 and L41, and the second pair of auxiliary inductors includes auxiliary inductors L32 and L42. The first pair of auxiliary inductors is shared by the first to 4th first circuit stages, and the second pair of auxiliary inductors is shared by the 5th to 7th first circuit stages. In some embodiments, the power conversion device further includes resonant inductors Lr32 and Lr42, where the resonant inductor Lr32 can be the leakage inductance of the auxiliary inductor L32 or an independent inductor connected in series with the auxiliary inductor L32, and the resonant inductor Lr42 can be the leakage inductance of the auxiliary inductor L42 or an independent inductor connected in series with the auxiliary inductor L42.

[0246] The corresponding first operating mode is as Figure 30 shown, where a branch formed by connecting the first capacitor C11 and the input capacitor Cin in series is connected in parallel with a branch formed by connecting the first capacitors C12 and C13 in series, and then connected in series with the auxiliary inductor L31 to form a first branch. A branch formed by connecting the second capacitors C22 and C21 in series is connected in parallel with a branch formed by connecting the second capacitors C24 and C23 in series, and then connected in series with the auxiliary inductor L41 to form a second branch. A branch formed by connecting the first capacitors C15 and C14 in series is connected in parallel with a branch formed by connecting the first capacitors C17 and C16 in series, and then connected in series with the auxiliary inductor L32 to form a third branch. A branch formed by connecting the second capacitors C26 and C25 in series is connected in parallel with the second capacitor C27 and then connected in series with the auxiliary inductor L42 to form a fourth branch. The first branch, the second branch, the third branch, and the fourth branch are connected in parallel, then connected in series with the second inductor L2, and then connected in parallel with the first inductor L1. There are eight equivalent capacitor circuits for transferring energy to the first inductor L1 and the second inductor L2. There are four equivalent capacitor-inductor circuits connected in parallel for transferring energy to the first inductor L1 and the second inductor L2.

[0247] The corresponding second working mode can be deduced in the same way, so it will not be elaborated here. From the first and second working modes, it can be deduced that when the power conversion device in this case has N = 7 (i.e., including seven first circuit stages) and p = 2 (i.e., including two pairs of auxiliary inductors), the ratio of the input voltage Vin to the output voltage Vo during the entire working cycle is (16 + 8Z)∶1.

[0248] According to Figures 26 to 30 the circuit topology of the power conversion device shown and its first and second working modes in the first mode and the second mode, and referring to Figure 8 and Figure 11 the general power conversion device shown when N is odd and even, the circuit topology of the general power conversion device and its first and second working modes when (N + 1) / p = 2 can be deduced.

[0249] Taking N being odd as an example, the corresponding first working mode is as shown in Figure 31 wherein, the branch formed by the series connection of the first capacitor C11 and the input capacitor Cin is connected in parallel with the branch formed by the series connection of the first capacitors C12 and C13 and then connected in series with the auxiliary inductor L31 to form the first branch; the branch formed by the series connection of the second capacitor C22 and C21 is connected in parallel with the branch formed by the series connection of the second capacitors C24 and C23 and then connected in series to the auxiliary inductor L41 to form the second branch. By analogy, the branch formed by the series connection of the first capacitors C1(N - 2) and C1(N - 3) is connected in parallel with the branch formed by the series connection of the first capacitors C1N and C1(N - 1) and then connected in series with the auxiliary inductor L3p to form the (2p - 1)th branch; the branch formed by the series connection of the second capacitors C2(N - 1) and C2(N - 2) is connected in parallel with the second capacitor C2N and then connected in series to the auxiliary inductor L4p to form the 2pth branch. The first inductor L1 and the second inductor L2 are connected in series to form the (2p + 1)th branch. The first to the (2p + 1)th branches are connected in parallel with each other.

[0250] The corresponding second working mode can be deduced in the same way, so it will not be elaborated here. From the first and second working modes, it can be deduced that when the power conversion device in this case has (N + 1) / p = 2, the ratio of the input voltage Vin to the output voltage Vo during the entire working cycle is (N + 1)*(2 + Z)∶1.

[0251] In addition, by the same token, the circuit topology of the general power conversion device and its first and second working modes when N = 5 (i.e., including five first circuit stages) and p = 1 (i.e., including a pair of auxiliary inductors and (N + 1) / p = 6) can also be deduced.

[0252] The corresponding first working mode is as shown in Figure 32As shown, a branch formed by series connection of a first capacitor C11 and an input capacitor Cin, a branch formed by series connection of first capacitors C12 and C13, and a branch formed by series connection of first capacitors C14 and C15 are connected in parallel and then connected in series with an auxiliary inductor L31 to form a first branch. A branch formed by series connection of a second capacitor C22 and C21, a branch formed by series connection of second capacitors C24 and C23, and a second capacitor C25 are connected in parallel and then connected in series with an auxiliary inductor L41 to form a second branch. The first branch and the second branch are connected in parallel, then connected in series with a second inductor L2, and then connected in parallel with a first inductor L1. There are six equivalent capacitor circuits for transferring energy to the first inductor L1 and the second inductor L2. There are two equivalent capacitor-inductor circuits connected in parallel for transferring energy to the first inductor L1 and the second inductor L2. The corresponding second operating mode can be deduced in the same way, so it will not be elaborated here.

[0253] According to the foregoing embodiments, and assuming that (N + 1) / p = k (k is a positive integer), the general first operating mode of the power conversion device can be deduced. Taking N being odd as an example, the corresponding general first operating mode is as Figure 33 shown. The corresponding general second operating mode can be deduced in the same way, so it will not be elaborated here.

[0254] In addition, in the foregoing embodiments, the power conversion device all includes paired auxiliary inductors. However, this case is not limited thereto. In some embodiments, the power conversion device may also include only one auxiliary inductor. Assume that the power conversion device includes one auxiliary inductor L31, and the auxiliary inductor L31 is shared by all the first circuit stages and the second circuit stages. When N = 3, the corresponding first operating mode is as Figure 34 shown, in Figure 34 which, a first capacitor C11 and an input capacitor Cin are connected in series to form a first branch, a second capacitor C22 and C21 are connected in series to form a second branch, and a first capacitor C13 and C12 are connected in series to form a third branch. The first branch, the second branch, the third branch and a second capacitor C23 are connected in parallel, then connected in series with an auxiliary inductor L31, then connected in series with a second inductor L2, and then connected in parallel with a first inductor L1. The corresponding second operating mode can be deduced in the same way, so it will not be elaborated here.

[0255] Furthermore, the general first operating mode of the power conversion device when it includes only one auxiliary inductor L31 can be deduced. Taking N being odd as an example, the corresponding general first operating mode is as Figure 35As shown, the first capacitor C11 of the first first circuit stage is connected in series with the input capacitor Cin to form a capacitive branch. The second capacitor C2i of the i-th first circuit stage is connected in series with the second capacitor C2(i + 1) of the (i + 1)-th first circuit stage to form another capacitive branch. The first capacitor C1j of the j-th first circuit stage is connected in series with the first capacitor C1(j + 1) of the (j + 1)-th first circuit stage to form yet another capacitive branch. All the capacitive branches and the second capacitor C2N of the N-th first circuit stage are connected in parallel with each other, then connected in series with the auxiliary inductor L31, then connected in series with the second inductor L2, and then connected in parallel with the first inductor L1. The corresponding second operating mode can be deduced in the same way, so it will not be elaborated here.

[0256] Please refer to Figure 36 , Figure 36 which is a schematic circuit diagram of the power conversion device of the sixth embodiment of this case. This is Figure 5 a variation of the power conversion device 1b shown, and it should be noted that Figure 36 the power conversion device 1f shown is not applicable to Figure 8 and Figure 11 the general power conversion devices shown. In Figure 36 , the elements with similar functions and structures to those in Figure 5 are denoted by the same reference numerals and will not be elaborated here. Compared with Figure 5 the power conversion device 1b shown, Figure 36 the positions of the first capacitor C11 and the second capacitor C21 of the first first circuit stage in Figure 36 are different, and the second circuit stage of the power conversion device 1f further includes a third inductor L3 and a fourth inductor L4. Specifically, as Figure 36 shown, in the power conversion device 1f, the second terminal of the first capacitor C11 of the first first circuit stage is changed to be electrically connected to the second terminal of the second switch S22 of the second first circuit stage, and the second terminal of the second capacitor C21 of the first first circuit stage is changed to be electrically connected to the second terminal of the first switch S12 of the second first circuit stage.

[0257] In the second circuit stage, the third inductor L3 is electrically connected between the second terminal of the third switch S3 and the third connection terminal P3, and the fourth inductor L4 is electrically connected between the second terminal of the fourth switch S4 and the fourth connection terminal P4. The third inductor L3 and the first inductor L1 are coupled to form a first coupled inductor, the fourth inductor L4 and the second inductor L2 are coupled to form a second coupled inductor, and the first coupled inductor and the second coupled inductor are coupled to each other.

[0258] When the power conversion device 1f operates in the first mode, the first switch S11, the second switch S22, the third switch S3, and the second rectifier switch SR2 are turned on, and the first switch S12, the second switch S21, the fourth switch S4, and the first rectifier switch SR1 are turned off. When the power conversion device 1f operates in the first mode, it forms Figure 37 the first operating mode shown. As Figure 37 shown, in the first operating mode, the third inductor L3 and the second capacitor C22 are connected in series to form a first branch, the first capacitor C11 and the input capacitor Cin are connected in series to form a second branch, and the first branch is connected in parallel with the second capacitor C21 and then connected in series to the second branch to form a third branch. The first capacitor C12 and the fourth inductor L4 are connected in series to form a fourth branch. The third branch and the fourth branch are connected in parallel with each other, then connected in series with the first inductor L1, and then connected in parallel with the second inductor L2.

[0259] When the power conversion device 1f operates in the second mode, the first switch S12, the second switch S21, the fourth switch S4, and the first rectifier switch SR1 are turned on, and the first switch S11, the second switch S22, the third switch S3, and the second rectifier switch SR2 are turned off. When the power conversion device 1f operates in the second mode, it forms Figure 38 the first operating mode shown. As Figure 38 shown, in the second operating mode, the fourth inductor L4 and the first capacitor C12 are connected in series to form a first branch, the second capacitor C21 and the input capacitor Cin are connected in series to form a second branch, and the first branch is connected in parallel with the first capacitor C11 and then connected in series to the second branch to form a third branch. The second capacitor C22 and the third inductor L3 are connected in series to form a fourth branch. The third branch and the fourth branch are connected in parallel with each other, then connected in series with the second inductor L2, and then connected in parallel with the first inductor L1.

[0260] Assume that the turns ratio of the first inductor L1 to the second inductor L2 is 1:1, the turns ratio of the third inductor L3 to the first inductor L1 is M:1, and the turns ratio of the fourth inductor L4 to the second inductor L2 is M:1, where M is a positive number. Based on this, it can be deduced that in the entire operating cycle of the power conversion device 1f, the ratio of the input voltage Vin to the output voltage Vo is (4M + 6):1. Furthermore, it can be deduced that the average value of the voltages on the first capacitor C11 and the second capacitor C21 of the first first - circuit stage is (2M + 2)*Vin / (4M + 6), and the average value of the voltages on the first capacitor C12 and the second capacitor C22 of the second first - circuit stage is (M + 2)*Vin / (4M + 6).

[0261] As Figure 39As described above, the power conversion device 1g includes at least two first circuit stages and a conversion unit. The at least two first circuit stages are connected in cascade, and each first circuit stage includes a switch and an energy storage element connected electrically. One of the first circuit stages receives the input voltage Vin, and periodically controls the switch in the first circuit stage, such that the energy storage element in each first circuit stage divides the input voltage to obtain an intermediate voltage, and the average value of the intermediate voltage within one period is less than or equal to 1 / 4 of the input voltage. The conversion unit receives the intermediate voltage and converts the intermediate unit into an output voltage. The conversion unit may correspond to the second circuit stage and the third circuit stage in the above embodiments, but the present invention is not limited thereto. The conversion unit may be a buck circuit, a half-bridge circuit, a full-bridge circuit or any other circuit that can implement conversion functions such as DC / DC or DC / AC. The intermediate voltage corresponds to the voltage at node T1 or T2.

[0262] It should be noted that the above is only a preferred embodiment proposed for the purpose of illustrating the present case. The present case is not limited to the described embodiment, and the scope of the present case is determined by the appended claims. And the present case can be variously modified by those skilled in the art, but all modifications shall not depart from the scope of protection of the appended claims.

Claims

1. A power conversion device, comprising: a positive input terminal and a negative input terminal for receiving an input voltage; a positive output terminal and a negative output terminal for providing an output voltage, wherein the negative input terminal is coupled to the negative output terminal; N first circuit stages, wherein each of the first circuit stages includes a pair of switches and a pair of energy storage elements connected electrically, and the pair of switches conduct complementarily, and the pair of energy storage elements have opposite operating states; a plurality of the energy storage elements in the N first circuit stages divide the input voltage, wherein N is an integer greater than or equal to 2; A second circuit stage, comprising a pair of switches that conduct complementarily; and a third circuit stage, including a pair of switches and a magnetic element connected electrically; wherein the N first circuit stages, the second circuit stage, and the third circuit stage are cascaded in sequence between the positive input terminal and the negative output terminal.

2. The power conversion device according to claim 1, wherein in each of the first circuit stages, the pair of switches includes a first switch and a second switch, the pair of energy storage elements includes a first energy storage element and a second energy storage element, and the first switch and the first energy storage element are electrically connected to a first node, and the second switch and the second energy storage element are electrically connected to a second node.

3. The power conversion device according to claim 2, wherein in the N first circuit stages, the N first switches are connected in series in sequence, and the N second switches are connected in series in sequence; the first energy storage element of any one of the first circuit stages is electrically connected to the second energy storage element of the adjacent first circuit stage.

4. The power conversion device according to claim 1, wherein within a switching period, each of the pair of switches in the N first circuit stages, the second circuit stage, and the third circuit stage includes a first-phase switch and a second-phase switch, the first-phase switch receives a switching signal of a first phase, and the second-phase switch receives a switching signal of a second phase; in each of the first circuit stages, the energy storage element corresponding to the first-phase switch in the pair of energy storage elements is a first-phase energy storage element, and the energy storage element corresponding to the second-phase switch in the pair of energy storage elements is a second-phase energy storage element.

5. The power conversion device according to claim 4, wherein when the first-phase switch conducts, the first-phase energy storage element is charged, and the second-phase energy storage element is discharged; when the second-phase switch conducts, the first-phase energy storage element is discharged, and the second-phase energy storage element is charged.

6. The power conversion device according to claim 4, wherein when the first-phase switch or the second-phase switch conducts, there are at least three branches for providing energy to the magnetic element, and each branch includes at least one energy storage element.

7. The power conversion device according to claim 4, wherein when the first-phase switch conducts, the first-phase energy storage element of the first one of the first circuit stages and an input capacitor are connected in series to form a first branch, the second-phase energy storage element of the i-th first circuit stage and the first-phase energy storage element of the (i + 1)-th first circuit stage are connected in series to form the (i + 1)-th branch, and the second-phase energy storage element of the N-th first circuit stage forms the (N + 1)-th branch, and the (N + 1) branches are connected in parallel to provide energy to the magnetic element, wherein i is a positive integer less than N.

8. The power conversion device as claimed in claim 4, wherein when the second-phase switch is turned on, the second-phase energy storage element of the first first circuit stage and an input capacitor are connected in series to form a first branch, the first-phase energy storage element of the i-th first circuit stage and the second-phase energy storage element of the (i + 1)-th first circuit stage are connected in series to form the (i + 1)-th branch, the first-phase energy storage element of the N-th first circuit stage forms the (N + 1)-th branch, and the (N + 1) branches are connected in parallel to supply energy to the magnetic element, where i is a positive integer less than N.

9. The power conversion device as claimed in claim 1, wherein the average value of the voltage on any energy storage element of the n-th first circuit stage is (N + 1 - n)*Vin / (N + 1), and the average value of the voltage on any energy storage element of the N-th first circuit stage is Vin / (N + 1), where n is a positive integer less than N.

10. The power conversion device as claimed in claim 1, wherein the ratio of the input voltage to the output voltage is 2(N + 1)∶1.

11. A power conversion device, comprising: a positive input terminal, a negative input terminal, a positive output terminal and a negative output terminal, wherein the negative input terminal is coupled to the negative output terminal; N first circuit stages, wherein each first circuit stage includes a first switch, a second switch, a first capacitor and a second capacitor, and has a first connection end and a second connection end, N is an integer greater than or equal to 2; the first ends of the first switch and the second switch of the first first circuit stage are both electrically connected to the positive input terminal, in any first circuit stage, the first end and the second end of the first capacitor are electrically connected to the second end of the first switch and the first connection end respectively, the first end and the second end of the second capacitor are electrically connected to the second end of the second switch and the second connection end respectively, the second end of the first switch of the n-th first circuit stage is further electrically connected to the first end of the first switch of the (n + 1)-th first circuit stage, the second end of the second switch of the n-th first circuit stage is further electrically connected to the first end of the second switch of the (n + 1)-th first circuit stage, where n is a positive integer less than N; the first connection end of the n-th first circuit stage is electrically connected to the second connection end of the (n + 1)-th first circuit stage, and the second connection end of the n-th first circuit stage is electrically connected to the first connection end of the (n + 1)-th first circuit stage; a second circuit stage, including a third switch and a fourth switch, and having a third connection end and a fourth connection end, wherein the first end and the second end of the third switch are electrically connected to the second end of the first switch of the N-th first circuit stage and the third connection end respectively, the first end and the second end of the fourth switch are electrically connected to the second end of the second switch of the N-th first circuit stage and the fourth connection end respectively, the third connection end is electrically connected to the second connection end of the N-th first circuit stage, and the fourth connection end is electrically connected to the first connection end of the N-th first circuit stage; and a third circuit stage, including: A first inductor and a second inductor are magnetically coupled to each other, wherein the first inductor is electrically connected between the second terminal of the third switch of the second circuit stage and the positive output terminal, and the second inductor is electrically connected between the second terminal of the fourth switch of the second circuit stage and the positive output terminal; A first rectifying unit is electrically connected between the second terminal of the third switch of the second circuit stage and the negative output terminal; and A second rectifying unit is electrically connected between the second terminal of the fourth switch of the second circuit stage and the negative output terminal.

12. The power conversion device according to claim 11, wherein the power conversion device operates alternately in a first mode and a second mode, In the first mode, the first switch of the x-th first circuit stage is turned on, the second switch of the x-th first circuit stage is turned off, the first switch of the y-th first circuit stage is turned off, the second switch of the y-th first circuit stage is turned on, x is an odd number greater than zero and less than or equal to N, y is an even number greater than 1 and less than or equal to N, and when N is odd, the third switch and the fourth switch of the second circuit stage are turned off and on respectively, and when N is even, the third switch and the fourth switch are turned on and off respectively; In the second mode, the first switch of the x-th first circuit stage is turned off, the second switch of the x-th first circuit stage is turned on, the first switch of the y-th first circuit stage is turned on, the second switch of the y-th first circuit stage is turned off, and when N is odd, the third switch and the fourth switch of the second circuit stage are turned on and off respectively, and when N is even, the third switch and the fourth switch are turned off and on respectively.

13. The power conversion device according to claim 12, further comprising an input capacitor, wherein two ends of the input capacitor are electrically connected to the positive input terminal and the negative input terminal respectively.

14. The power conversion device according to claim 13, wherein, When N is odd, the power conversion device forms a first working mode when operating in the first mode; in the first working mode, the first capacitor of the first circuit stage is connected in series with the input capacitor to form a capacitor branch, the second capacitor of the i-th first circuit stage is connected in series with the second capacitor of the (i + 1)-th first circuit stage to form another capacitor branch, the first capacitor of the j-th first circuit stage is connected in series with the first capacitor of the (j + 1)-th first circuit stage to form yet another capacitor branch, i is an odd number greater than zero and less than N, j is an even number greater than 1 and less than N, the first inductor and the second inductor are connected in series to form an inductor branch, the first end of the first inductor is connected to the second inductor and the positive output terminal, the second end of the first inductor is connected to the negative output terminal, and all the capacitor branches, the inductor branch and the second capacitor of the N-th first circuit stage are connected in parallel with each other.

15. The power conversion device according to claim 13, wherein, When N is odd, the power conversion device forms a second operating mode when operating in the second mode; in the second operating mode, the second capacitor of the first circuit stage is connected in series with the input capacitor to form a capacitor branch, the first capacitor of the i-th first circuit stage is connected in series with the first capacitor of the (i + 1)-th first circuit stage to form another capacitor branch, the second capacitor of the j-th first circuit stage is connected in series with the second capacitor of the (j + 1)-th first circuit stage to form yet another capacitor branch, where i is an odd number greater than 0 and less than N, j is an even number greater than 1 and less than N, the first inductor and the second inductor are connected in series to form an inductor branch, the first end of the second inductor is connected to the first inductor and the positive output terminal, the second end of the second inductor is connected to the negative output terminal, and all the capacitor branches, the inductor branch, and the first capacitor of the N-th first circuit stage are connected in parallel with each other.

16. The power conversion device according to claim 13, wherein, When N is even, the power conversion device forms a first operating mode when operating in the first mode; in the first operating mode, the first capacitor of the first circuit stage is connected in series with the input capacitor to form a capacitor branch, the second capacitor of the i-th first circuit stage is connected in series with the second capacitor of the (i + 1)-th first circuit stage to form another capacitor branch, where i is an odd number greater than 0 and less than N; if N is greater than 3, the first capacitor of the j-th first circuit stage is connected in series with the first capacitor of the (j + 1)-th first circuit stage to form yet another capacitor branch, where j is an even number greater than 1 and less than N; the first inductor and the second inductor are connected in series to form an inductor branch, the first end of the second inductor is connected to the first inductor and the positive output terminal, the second end of the second inductor is connected to the negative output terminal; and all the capacitor branches, the inductor branch, and the first capacitor of the N-th first circuit stage are connected in parallel with each other.

17. The power conversion device according to claim 13, wherein, When N is even, the power conversion device forms a second operating mode when operating in the second mode; in the second operating mode, the second capacitor of the first circuit stage is connected in series with the input capacitor to form a capacitor branch, the first capacitor of the i-th first circuit stage is connected in series with the first capacitor of the (i + 1)-th first circuit stage to form another capacitor branch, where i is an odd number greater than 0 and less than N; if N is greater than 3, the second capacitor of the j-th first circuit stage is connected in series with the second capacitor of the (j + 1)-th first circuit stage to form yet another capacitor branch, where j is an even number greater than 1 and less than N; the first inductor and the second inductor are connected in series to form an inductor branch, the first end of the first inductor is connected to the second inductor and the positive output terminal, the second end of the first inductor is connected to the negative output terminal; and all the capacitor branches, the inductor branch, and the second capacitor of the N-th first circuit stage are connected in parallel with each other.

18. The power conversion device according to claim 12, wherein in one operating cycle of the power conversion device, the duration for which the power conversion device operates in the first mode is less than or equal to half of the operating cycle, and the duration for which the power conversion device operates in the second mode is less than or equal to half of the operating cycle.

19. The power conversion device according to claim 11, wherein the first capacitor and the second capacitor of each of the first circuit stages are resonant capacitors and are configured to resonate with a first resonant inductor and a second resonant inductor. The first resonant inductor is the leakage inductance of the first inductor or an inductor connected in series with the first inductor, and the second resonant inductor is the leakage inductance of the second inductor or an inductor connected in series with the second inductor.

20. The power conversion device according to claim 19, wherein a resonant frequency at which the resonant capacitor resonates with the first resonant inductor and the second resonant inductor is equal to the switching frequency of the first switch and the second switch of each of the first circuit stages.

21. The power conversion device according to claim 11, wherein an end of the first inductor connected to the positive output terminal and an end of the second inductor connected to the positive output terminal are of opposite polarities.

22. The power conversion device according to claim 11, wherein the first inductor and the second inductor form a transformer.

23. The power conversion device according to claim 11, wherein, In one operating cycle of the power conversion device, the effective value of the current flowing through the first inductor is substantially equal to the effective value of the current flowing through the second inductor.

24. The power conversion device according to claim 11, wherein the first rectification unit includes a first rectification switch, and the second rectification unit includes a second rectification switch.

25. The power conversion device according to claim 11, wherein the average value of the voltages on the first capacitor and the second capacitor of the nth first circuit stage is both (N + 1 - n)*Vin / (N + 1), and the average value of the voltages on the first capacitor and the second capacitor of the Nth first circuit stage is both Vin / (N + 1).

26. The power conversion device according to claim 11, wherein the positive input terminal and the negative input terminal are configured to receive an input voltage, and the positive output terminal and the negative output terminal are configured to provide an output voltage; the turns ratio of the first inductor to the second inductor is 1, and the ratio of the input voltage to the output voltage is 2(N + 1):

1.

27. The power conversion device according to claim 11, wherein the positive input terminal, the negative input terminal, the positive output terminal, the negative output terminal, the N first circuit stages, the second circuit stage, and the third circuit stage form a power conversion module; the power conversion device includes a plurality of such power conversion modules, and the positive input terminals of the plurality of power conversion modules are connected together, the negative input terminals of the plurality of power conversion modules are connected together, the positive output terminals of the plurality of power conversion modules are connected together, and the negative output terminals of the plurality of power conversion modules are connected together.

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